Module eqstate -- the equation of state


INTERFACE:

   MODULE eqstate
DESCRIPTION:

Computes the density, $ {\langle \rho \rangle} $, and buoyancy from the salinity, $ S$, the temperature, $ \Theta$, and the thermodynamic pressure, $ P$, according to an equation of state,

$\displaystyle {\langle \rho \rangle} = \hat{\rho} (S,\Theta,P) \quad .$ (244)

The following remark on the thermodynamic interpretation of density, temperature, and pressure is useful here. If $ \Theta$ is identified with the in-situ temperature, and $ P$ with the in-situ pressure, then $ {\langle \rho \rangle} $ will be the in-situ density. On the other hand, if $ P$ is identified with the surface pressure, and $ \Theta$ with the potential temperature, the same equation of state, (244), will yield $ {\langle \rho \rangle} $ as the potential density. Note that the quantity sigma_t found in the GOTM output is simply computed from $ {\langle \rho \rangle} $ - 1000 kg m$ ^{-3}$, and may therefore adopt different meanings.

At present, two different models for the equation of state ("modes"), and four different "methods" how to evalute the equation of state are implemented.

Modes:

  1. The UNESCO equation of state according to Fofonoff and Millard (1983)
  2. The Jackett et al. (2005) equation of state
Methods:
  1. the full equation of state -- including pressure effects
  2. the full equation of state -- without pressure effects
  3. the linearised equation of state
  4. a general linear form of the equation of state


USES:

   IMPLICIT NONE
 
   default: all is private.
   private
PUBLIC MEMBER FUNCTIONS:
   public init_eqstate,eqstate1,eos_alpha,eos_beta,unesco,rho_feistel
REVISION HISTORY:
   Original author(s): Hans Burchard & Karsten Bolding



Subsections
Karsten Bolding 2012-12-28